1. Field of Invention
The present invention relates to an electromagnetic valve. More particularly, the present invention relates to an electromagnetic pressure relief valve.
2. Description of Related Art
FIG. 1 illustrates a cross-sectional view of a conventional pressure relief valve. An air faucet 120 of the pressure relief valve 100 is coupled with a pipe, which needs to release its pressure. In a release mode of the pressure relief valve 100, a resilient force of the spring 112 is to prevent the gasket 106 from contacting or sealing the air opening 114a such that the pressure relief valve 100 can release air pressure via the air opening 114a. In a sealing mode of the pressure relief valve 100, the coil wire 110 of the pressure relief valve 100 is electrified, the ferromagnetic stopper 108 and the ferromagnetic cylinder 114 attract each other to against the resilient force of the spring 112 so as to push the gasket 106 against the air opening 114a, namely, the air pressure is not released via the air opening 114a. 
In this conventional pressure relief valve 100, the air faucet 120 and the ferromagnetic cylinder 114 are of a single unitary metallic piece, i.e., a ferromagnetic cylinder, namely, the air opening 114a is formed on the ferromagnetic cylinder 114. In order to enable the air opening 114a to be easily sealed by the gasket 106, the air opening 114a needs to be precisely manufactured. Because the manufacturing costs for forming the air opening on the ferromagnetic cylinder is high, the total cost of the pressure relief valve 100 is hardly lowered.